| With the rapid development of the high-speed railway in China,the traction load of the railway is getting heavier,and the requirements for the reliability and power supply capacity of traction power supply system are becoming higher and higher.In recent years,there have been many reports about problems such as insufficient power supply capacity of the traction network,excessively high transmission wire temperature of traction network,and the low voltage at the locomotive terminal in China.Only by clarifying the power supply capacity of the traction network and the distribution of the power flow can the traction power supply system design,load dispatch,and operation and maintenance be carried out reasonably,and the transmission capacity of the traction network can be fully utilized to ensure the safe and efficient operation of the traction power supply system.The temperature of the transmission wire of the traction network is affected by current-carrying and geographical and climatic factors,and the resistance parameter of the transmission wire is related to the temperature of the wire,so the resistance parameter of the transmission wire of the traction network changes during the actual operation.Existing traction network power flow calculations pay more attention to the model establishment and algorithm research,without considering the change of the transmission wire resistance parameters of the traction network,which affects the accuracy of the power flow calculation results.Different geographical and climatic conditions have a different current-carrying capacity when the transmission wires of the traction network reach the maximum allowable temperature.The rated current carrying capacity of transmission wire in traction network is calculated under specific meteorological conditions,and the occurrence probability of such specific meteorological condition is very low.The traction network has a long wire and a large span,and the climatic parameters are different in different places,seasons and times.Therefore,the current-carrying capacity of the traction network can be dynamically calculated according to the real-time meteorological parameters of the location of the traction network to achieve the purpose of dynamic capacity increase.Based on the electric-thermal coupling theory of transmission wires,this dissertation proposes a method for power flow calculation and a dynamic capacity increase of traction network.The main research work is as follows:(1)The electro-thermal coupling theory of transmission wires in traction network.The theoretical framework of electro-thermal coupling of transmission wire is the basis of this dissertation.Firstly,the heat balance equation of the traction network transmission wire is analyzed.Secondly,the influencing factors of the heat balance equation are analyzed.Thirdly,the geographical and climatic characteristics of Lhasa,Lanzhou and Nanjing are analyzed,and the value and variation range of geographical and climatic factors which have a great influence on the electro-thermal coupling are summarized,which are used as the basic data for the climatic parameters of this dissertation.Finally,the relationship between the resistance of the contact wire of the traction network and the change of the current-carrying and the geographical and climatic conditions is analyzed in the form of a calculation example.The results show that the geographical and climatic parameters that affect the temperature and resistance of transmission wires include ambient temperature,wind speed,wind direction angle,light intensity,air density,altitude,etc.(2)Power flow calculation of traction network considering the influence of electro-thermal coupling.To make the power flow calculation result of the traction network more accurate and practical,the electro-thermal coupling theory is introduced into the power flow calculation of the traction network,and a power flow calculation method considering the influence of electro-thermal coupling is proposed.Firstly,the power supply mode of the traction network is analyzed,and the unified power flow calculation model of the traction network is established.Secondly,the calculation method and implementation process of power flow considering the influence of electro-thermal coupling is proposed.Finally,taking the climatic conditions of Lhasa and Nanjing as an example,the calculation results of the power flow of the traction network under different geographical and climatic conditions are compared and analyzed.The research results show that the change of resistance parameters of transmission wires in traction network has a great influence on the calculation results of traction network power flow,and the change of resistance parameters of transmission wires should be considered in the process of power flow calculation.(3)Calculation of carrying capacity and dynamic thermal rating of traction network.The current carrying capacity of transmission wires is the main factor to be considered in the process of wire selection and load dispatching,and the carrying capacity is affected by the geographical and climatic factors of the traction network.Firstly,the calculation method of single transmission wire current carrying capacity and traction network comprehensive current carrying capacity considering the influence of geographical and climatic factors is analyzed.Secondly,the method of transmission wire matching and dynamic thermal rating is proposed.Finally,an example is given to illustrate the effect of current-carrying capacity of the traction network and dynamic thermal rating.The results show that different geographical and climatic conditions have a great influence on the current carrying capacity of transmission wires.The matching degree of the selected transmission wire can be judged by the capacity utilization rate of the transmission wire.The current carrying capacity of the traction network can be greatly improved by the technology of dynamic thermal rating.The research results have certain reference significance for the selection of transmission wires and load dispatching in traction network.(4)Current carrying capacity prediction of transmission wire in traction network.In the actual traction load dispatching process,it is often necessary to plan.According to the existing data,predicting the current carrying capacity of the traction network transmission wire is of great significance to the traction load dispatching.In this dissertation,the improved GM(1,1)model is used to predict the current carrying capacity of the transmission wire in the traction network.Firstly,the grey GM(1,1)model and its improvement methods are analyzed.Secondly,the current-carrying prediction method and its implementation process integrating multiple improvements are proposed.Finally,an example is given to illustrate the effectiveness of the current-carrying capacity prediction method.The research results show that the deviation between the current-carrying capacity predicted by the improved GM(1,1)model and the actual current carrying capacity is small,which can be used as the theoretical basis for the planning of traction load dispatching.(5)Reliability analysis of traction power supply relay protection system considering the influence of capacity increase.Dynamic capacity increase of traction network is to dynamically increase the rated load capacity of traction network under the premise that the transmission wire temperature does not exceed the maximum allowable temperature.However,whether the dynamic capacity increase will affect the relay protection system needs to be studied.Firstly,the configuration of traction power supply relay protection system and the possible influence of capacity increase on relay protection are analyzed.Secondly,the reliability analysis model of the traction power relay protection system is established.Finally,the calculation method and realization process of relay protection reliability scoring based on the fuzzy analytic hierarchy process is proposed,and the reliability scoring grades are divided.The research results show that the evaluation method can score and evaluate the reliability level of each relay protection,and pay more attention to the relay protection devices with the scoring level of "medium" or below,which provides a reference for railway operation and maintenance personnel.Based on the theoretical framework of electro-thermal coupling of transmission wires,this dissertation forms a theoretical system including power flow calculation,dynamic capacity increase,current-carrying capacity prediction and reliability analysis of relay protection system considering the influence of electro-thermal coupling.On the premise of safety and reliability of the system,the capacity utilization rate of the transmission wire of the traction network is effectively improved,which can bring obvious economic and social benefits. |
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